Manufacture of chloropyrenes



Patented June 28, 1949 MANUFACTURE OF CHL OROPYRENES Peter George Garter, Manchester, England, 2as-,

signor to lmperial Chemical Industries Limited, a corporation 'of Great Britain No Drawing. Application December 4, 1945, Se-

rial No. 632,789. In Great Britain. December'l,

l 4 Claims. (Cl. 260-649) This invention relates to the manufacture of chloropyrenes and more particularly it relates to-the manufacture of chloropyrenes containing 3 to 4 chlorine atoms from pyrene-containing coal products.

It is known that certain fractions of coal-tar, of hydrogenated coal-tar and of hydrogenated coalcontain small quantities of pyrene. The'separation of this pyrene .ona commercial scale, particularly from fractions containing very small quantities of pyrene, has hitherto presenteddifiiculties arising'from the similarity between the physical properties of pyrene and those of the other constituents of the pyrene-containing fractions.

It'is also known that triand tetra-chloropyrenes may readily be made by chlorination of pyrene but owing to the difficulties attendant on the separation of pyrene from the pyrene-containing fractions triand tetra-chloropyrenes have hitherto been relatively inaccessible materials.

This invention is based on the discovery that it is unnecessary'in the manufacture of triand tetra-chloropyrenes or of mixtures of these substances frompyrene-containing fractions of coaltar of hydrogenated coal-tar or of hydrogenated coal toisolate the pyrene.

According to the invention we. provide aprocess for the manufacture of triand tetra-chloropyrenes or of mixtures of these substances by chlorinating pyrene-containing, fractions of coal-tar, of hydrogenated coal-tar or of hydrogenated-coal. characterised in that thechlorination is carried out in an inert organic solvent. in. which the chloropyrenes are substantially insoluble at least at atmospheric. temperature, but in which preferably the remaining material is soluble, the chloro-pyrenes being separated from the reaction mixture by cooling and filtering.

The pyrene-containing fractions which may be used in the process of the invention include for example fractions of heavy creosote oil, of hydrogenated creosote oil and of heavy anthracene oil but any fraction of coal-tar, of hydrogenated coaltar, or of hydrogenated coal may be used provided there is pyrene present therein. Chloropyrenes have been obtained by the process of the invention from fractions containing as little as 2% by weight of pyrene.

The chlorination is effected directly, by the passage of chlorine gas into the solution of the pyrene-containing fraction in a suitable solvent. The temperature at which the chlorination is conducted may vary and atmospheric temperature is suitable but it has been found advantageous, prior to-the commencementof chlorination, to heat the reaction mixture in a bath. at about C. In order toobtain the best results chlorine should be passed in rapidly, for example at a speed of 20 litres per hour per 100 grams of fraction.

Theorganic solvent used, as said, is inertgthat is to say it is a solvent which will not itself be appreciably chlorinated under the conditions of the process. It should be one in which at at.- mospheric-temperature triortetra-chloropyrene or mixtures of these substances are substantially insoluble and, preferably, in which the other material present, both before and after chlorination, is readily soluble. Suitable solvents which have been used successfully include nitrobenzene, bromobenzene, a-chloronaphthalene, .tetrachloroethane, benzene, carbon tetrachloride, acetic acid, and. o-dichlorobenzene. It may be determined whether a given solvent is suitable by a laboratory small-scale trial.

The proportion of pyrene-containing fraction to solvent is conveniently as high .as 1 to 2 or 3by weight inorder. that the best yields of chloropyrenesmay beobtained. The duration of the passage of chlorine through the reaction mixture, may be determined by coolingand filtering off the separated solid from a test-portion of the reaction mixture. When the so-isolated solid does not begin to melt below 310 C. the chlorinationis complete. Under certain conditions and particularly when the proportion of pyrene in the pyrenecontaining, fraction'used is fairly high e. g. of the order of 10% by weight it has been found that a record of the temperature. changes within the reactionmixturewill give an indication of the completion 'of. chlorination since it is observed thatthe saidtemperature on commencement of chlorination rises steadily and subsequently falls this fall being followed by a second rise which is accompanied by separation of the chloropyrenes. When the temperature begins to fall a second time the formation of chloro-pyrenes is complete and chlorination may be discontinued.

The separated solid deposit of chloropyrenes may be filtered from the residual liquid material after cooling the reaction mixture to about atmospheric temperature. It may thereupon be washed, conveniently first with the solvent used in the chlorination, and preferably subsequently with anotherlower boiling solvent for example ethanol, and then dried.

When, for example, acetic acid or carbon tetrachloride is used as the solvent the residue may be tarry owing to separation of some insoluble matter 3 other than chlorinated pyrene. In this event the tarry matter may be removed by washing with for example benzene.

The so-obtained product consists of tetrachloropyrene containin variable proportions of trichloropyrene. It is useful for example in the manufacture of higher polychloropyrenes and of naphthalene-1 :4 :5 :8-tetracarboxylic anhydride which are themselves useful as intermediates in the manufacture of vat dyestuffs.

The invention is illustrated but not limited by the following examples in which the parts are by weight:

Example 1 100 parts by weight of a fraction (B. P. 215- 245 C./l3 mm.) of heavy creosote oil are dissolved in 300 parts of nitrobenzene, and the mixture is stirred in a boiling water-bath. Chlorine gas is introduced into the solution through a wid tube which dips below the surface of the stirred solution, at a speed of 22-24 litres per hour per 100 grams of fraction. The temperature of the mixture rises, then falls, then again rises; as soon as the temperature begins to fall for the second time the current of chlorine is discontinued. The mixture is stirred in the boiling water-bath for a further 15 minutes, then cooled to 20-30 C., and filtered. The solid residue is washed with nitrobenzene, then with ethanol, and dried. There are obtained 8.22 parts of a cream-coloured solid, M. P. 310-355 0., consisting of a mixture of triand tetrachloropyrene.

, Example 2 A mixture of 100 parts of the fraction of B. P. 380-400 C. of heavy anthracene oil and 200 parts of nitrobenzene is chlorinated as described in Example 1. 11.4 parts of a mixture of triand tetra-chloropyrene are obtained.

Example 3 A mixture of 200 parts of nitrobenzene and 100 parts of the fraction of B. P. 215-245 C./13 mm. of hydrogenated creosote oil is chlorinated as described in Example 1. 21.8 parts of a mixture of triand tetra-chloropyrene are obtained.

Example 4 A mixture of 200 parts of commercial dichlorobenzene and 100 parts of fraction (B. P. 215-245 C./ 13 mm.) of heavy creosote oil is chlorinated as described in Example 1. 6.96 parts of a mixture of triand tetra-chloropyrene are obtained.

Example 5 A mixture of 300 parts of nitrobenzene and 100 parts of the fraction of B. P. 215-245 C./1 3 mm. of heavy anthracene oil is chlorinated as mie, vol. 4, pages 237-242 4 described in Example 1, but at a rate of 7-8 litres of chlorine per hour per g. of fraction. 15.8 parts of a mixture of triand. tetra-chloropyrene are obtained.

I claim:

1. A process for the recovery of pyrene in the form of triand tetra-chloropyrenes from fractions of coal tar, hydrogenated coal tar and hydrogenated coal and the production of such chloropyrenes, which comprises passing chlorine into an organic solvent solution of the pyrene containing fraction unti1 the formation of the chloropyrenes in the solution is substantially complete and separating the resulting chloropyrenes from the reaction mixture by cooling and filtering, the organic solvent employed being one which is inert under the conditions of chlorination and in which the chloropyrenes are substantially insoluble at atmospheric temperatures but in which the pyrene containing fraction, from which the pyrene is being extracted in the form of chloropyrenes, is soluble.

2. The process as defined in claim 1 in which the inert solvent is a chlorinated hydrocarbon.

3. The process as defined in claim 1 in which the inert solvent is nitrobenzene.

4. A process for the recovery of pyrene in the form of triand tetra-chloropyrene from fractions of coal tar, hydrogenated coal tar and hydrogenated coal and the production of such chloropyrenes, which comprises passing chlorine into a nitrobenzene solution of the pyrene containing fraction while it is maintained at boiling water bath temperature until the formation of the chloropyrenes in the solution is substantially complete and separating the resulting chloropyrene from the reaction mixture by cooling and filtering, the amount of nitrobenzene employed being, by weight, from 2 to 3 times that of the pyrene containing fraction.

PETER GEORGE CARTER.

REFERENCES CITED The following referenlces are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,018,935 Vollmann et al. Oct. 29, 1935 2,094,227 Wolfram et al. Sept. 28, 1937 OTHER REFERENCES Beilstein: Handbuch der Organischen Chemie, vol. 5, page 694.

Goldschmiedt et al.: Monatshefte fiir Che- (1883). Grundlegende Operationen 4th ad, page (1938).

Fierz-David et al.: der Farbenchemie, 

